The principal philosophy of the Borg Collective was a drive towards achieving a state of "perfection" for themselves and, in their view, all life. The Borg achieved their "perfection" in several ways, all of which assimilated the individual into the greater hive mind of the collective.

Their other method was the forcible and usually violent assimilation of other lifeforms and technologies to enhance the biological and technological distinctiveness of the Collective. This was necessary for the Borg to innovate, adapt, and incorporate both the beneficial physiological and technological achievements of the assimilated species and was their principal method of expansion; they were otherwise unable to independently improve themselves and could neither understand nor mimic that which they did not assimilate. (This limitation was responsible for their inability to devise any countermeasures against Species 8472.) They would then distribute such new benefits and knowledge throughout the Collective via a network of a collective consciousness. Thus, by combining the advantages of myriad species, they sought to bring themselves and the rest of life closer to an integrated, homogeneous, "perfected" state. A not-inconsequential side effect of this was the elimination of the individuality and autonomy of its members ("drones") and thus a fierce resistance to the Borg by all other species. (VOY: "Dark Frontier", "Unimatrix Zero")

While in general the Borg tried to assimilate most species, they were in fact highly discriminating with respect to which species they would assimilate: those deemed unfit for enhancing the Borg Collective were either ignored or, if they posed a threat, destroyed. Seven of Nine told Neelix that the Kazon were "unworthy" of assimilation and would only detract from the Borg's quest for perceived perfection. (VOY: "Mortal Coil")

When summarizing their worldview and its effects in a general terminology, the entity Q described the Borg as "the ultimate users," and their chosen targets for assimilation as things "they can consume." (TNG: "Q Who"; Star Trek: First Contact)

It is unclear what Q meant by "ultimate users". In addition, the Borg later seemed to change their goal of assimilating that which "they can consume" to a much more discriminating selection process. This could be explained by the time lag between the events in "Q Who" and "Mortal Coil" and a subsequent change in the Borg's philosophy and/or assimilation techniques. On the other hand, Q's description of Borg philosophies and methods could have been subjective to how the Continuum perceived them.

To the Borg, the concept of death was an irrelevant idea in their philosophy. (TNG: "The Best of Both Worlds") Instead of elaborate rituals or burials, when a drone was damaged beyond repair, it was simply discarded. All of its experiences and memories continued to live on inside the collective consciousness. This was considered a form of immortality by the Borg. (VOY: "Mortal Coil")

The Borg viewed the significant practical benefits conferred by assimilation as both desirable for themselves and the victim species; they seemed to genuinely fail to comprehend what they saw as the narrow-minded resistance shown toward assimilation and its attendant loss of individuality of the other species. Freedom, self-determination, and individual rights were viewed as archaic concepts necessary only to less advanced, authority-driven cultures, as noted by Locutus. (TNG: "The Best of Both Worlds", "The Best of Both Worlds, Part II")

Later, the Borg Queen variously described former Borg drone Seven of Nine's new-found individuality as both a strength and "weakness", though the former was from Seven's unique ability to bring a greater understanding of individuality to the Borg to aid their quest to assimilate Humanity. The Queen also attempted to explain the Borg Collective in innocuous terms to a child by describing it as a place where everyone were "friends." (VOY: "Dark Frontier", "Unimatrix Zero")

While working towards perfecting themselves through assimilation, the Borg rejected certain species they perceived would detract from their goal. In other cases, the Borg specifically targeted a species considered especially qualified to assist in achieving it. As mentioned above, the Kazon of the Delta Quadrant were an example of the former, as Seven later testified to USS Voyager crewman Neelix, "Their biological and technological distinctiveness was unremarkable; they were unworthy of assimilation." (VOY: "Mortal Coil")

As an example of the latter, the Borg repeatedly went to great lengths – including two frontal assaults and even time-travel (TNG: "The Best of Both Worlds"; Star Trek: First Contact) – to assimilate Humanity, even though the Borg Queen described their physiology as "unremarkable" and deficient. Nonetheless, the Queen recruited Seven to develop a pathogen that would surreptitiously and slowly assimilate Humanity, as those previous direct attempts had failed. (VOY: "Dark Frontier")

Jean-Luc Picard had earlier confirmed this view of the Human race as an example of a species desirable for assimilation, believing his assimilation to have been an attempt "... to bridge the gulf between Humanity and the Borg." (Star Trek: First Contact)

The Borg considered Particle 010, known as the "Omega molecule" to Starfleet, to be an expression of perfection (in effect, a technological "holy grail") and were willing to pay any price to assimilate it. The only current or former member of the Collective known to have witnessed this perfection was Seven of Nine, who saw the spontaneous stabilization of several Omega molecules in a harmonic resonance chamber while aboard the Voyager, an experience Kathryn Janeway subsequently described as the equivalent of a spiritual experience for Seven. (VOY: "The Omega Directive")

The Borg were essentially amoral, neither wishing to inflict undue pain upon others nor hesitating to do so when necessary. According to Arturis, whose people had been mostly assimilated (in essence, wiped out), the Borg were no more guilty than a "force of nature," similar to a hurricane. When discussing their alliance with the Borg in their war with Species 8472, Chakotay made a similar reference to the amoral nature of the Borg by reciting the story of the scorpion and the fox. He likened the Borg's inability to embrace traditional morals, such as trust, as a mere morally-neutral artifact of their nature. (VOY: "Hope and Fear", "Scorpion")

When the USS Enterprise-D crew discovered a band of disconnected, "rogue" Borg under the leadership of Lore, they were initially shocked to see these Borg act with both emotions and a sense of (im)morality, further indicating by way of contrast the Borg's usual amoral, dispassionate behavior. (TNG: "Descent")

Unlike most other belligerent species, the Borg did not invest themselves emotionally in their conflicts: in all their conquests, they displayed a straightforward, dispassionate goal of assimilating other species to add to their own perfection. In fact, they would ignore "enemy" ships and individuals unless they perceived them to be either a threat or useful for assimilation. The Borg also did not seek revenge or desire to settle vendettas against others. (VOY: "The Raven", "Dark Frontier", "Unimatrix Zero"; TNG: "Q Who", "The Best of Both Worlds", "Descent", et al.)

This dispassion, while in some ways preferable to an enemy who wishes to exact revenge, torture, or pain upon its enemies, nonetheless added to most humanoids' perception of the Borg as an emotionless, mechanistic species and added an unsettling quality to them: though the Borg did not go out of their way to inflict harm or barbarity, it was not possible to appeal to them for compassion, reason, or other typical, humanoid characteristics. An example of this was their lack of interest in the possibility of destroying the Kazon species and seize their (unsatisfactory but still numerous) assets and population, as mentioned above. This was also demonstrated when Captain Janeway attempted to forge a temporary alliance with the Borg that would have been mutually beneficial to both, during the Borg's war with Species 8472: the Borg were unable to resist their tendency to attempt to assimilate Voyager, even though it was not in their best long-term interest. (VOY: "Scorpion")

Michael Eddington, the disaffected former Starfleet officer who became a prominent leader of the rebellious Maquis, once unfavorably compared the United Federation of Planets' philosophy of adding new member species and worlds to that of Borg assimilation. He suggested the relative homogenization process effectively enforced upon all UFP member worlds was not unlike that undergone by assimilated Borg drones. Furthermore, he asserted that the Federation's apparent intolerance for its citizens to voluntarily secede was not unlike how the Borg denied its drones the choice of leaving the Collective.

In both cases, suggested Eddington, neither the UFP nor the Collective could countenance that any of its population would willingly choose to leave "paradise" – Eddington's ironic derogatory description of the UFP – or the "perfection" offered by the Borg. Indeed, in Eddington's view, the UFP was more "insidious" than the Borg, for unlike the latter, the Federation did not explicitly announce their intent to "assimilate", instead doing it surreptitiously yet with similar results. (DS9: "For the Cause")

Although these sentiments represented the viewpoint of prominent Maquis leader Michael Eddington, it is uncertain whether or how many of his fellow Maquis believed the Federation and the Borg Collective shared such a common, "assimilation"-based philosophy. Comments made by a Romulan Tal Shiar agent, however, in the non-canon Section 31 novel Rogue, might be taken as apocryphal evidence that other political powers outside the Federation might also profess such an opinion.

Locutus of Borg told Worf in TNG: "The Best of Both Worlds, Part II" that the Borg sought to improve the quality of life for all species. Seven of Nine in VOY: "Mortal Coil", however, provided a seemingly different explanation when she described the Borg's lack of desire to assimilate the (apparently unworthy) Kazon species. Her statements indicated the Borg were interested only in assimilating species they believed would improve their own technological and biological distinctiveness in their quest for perfection. A complete understanding, however, of Borg theories on such advancement-through-assimilation is difficult to attain from the few canonical references regarding the matter.

A possible reconciling interpretation is that the Borg simply had no urgency in assigning any priority to assimilating the Kazon; perhaps they believed they would effect ultimate gain for species deemed otherwise unworthy of assimilation via the homogenizing, perfecting expansion (and the attendant extinction of lesser species) of the Collective. Another possible explanation, stated above, is that the Borg changed their philosophy and/or assimilation techniques in the interim between the two episodes. Finally, it is possible the two statements were made under differing motives and that Locutus was trying to mollify the Enterprise-D crew by lying.